IfcTrapeziumProfileDef defines a trapezium as the profile definition used by the swept surface geometry or the swept area solid. It is given by its Top X and Bottom X extent and its Y extent as well as by the offset of the Top X extend, and placed within the 2D position coordinate system, established by the Position attribute. It is placed centric within the position coordinate system, that is, in the center of the bounding box.

HISTORY  New entity in IFC1.5. The use definition has changed in IFC2x.

Figure 577 illustrates parameters of the trapezium profile definition.

Position The parameterized profile defines its own position coordinate system. The underlying coordinate system is defined by the swept surface or swept area solid that uses the profile definition. It is the xy plane of either: IfcSweptSurface.Position IfcSweptAreaSolid.Position or in case of sectioned spines the xy plane of each list member of IfcSectionedSpine.CrossSectionPositions. By using offsets of the position location, the parameterized profile can be positioned centric (using x,y offsets = 0.), or at any position relative to the profile. Explicit coordinate offsets are used to define cardinal points (e.g. upper-left bound). Parameter The IfcTrapeziumProfileDef is defined within the position coordinate system, where the BottomDim defines the length measure for the bottom line (half along the positive x-axis) and the YDim defines the length measure for the parallel distance of bottom and top line (half along the positive y-axis). The top line starts with a distance of TopXOffset from [-BottomLine/2,YDim] (which can be negative, zero, or positive) and has a length of TopXDim along the positive x-axis.

Figure 577 — Trapezium profile